Ketoisophorone is valued as an intermediate in the production of drugs and perfumes, and can be obtained via the oxidation of alpha-IP (by alpha-IP applicants mean isophorone that is predominately or completely in the alpha form). Numerous procedures have been developed to accomplish this oxidation. In U.S. Pat. No. 3,931,327 a two step process was used to convert isophorone to KIP. The first step is the conversion of alpha-IP to its isomeric form, beta-IP (3,5,5-trimethyl-3-cyclohexenone). In the second step, the beta-IP is converted to KIP by passing molecular oxygen through the beta-IP in the presence of a metal catalyst and an organic base. However, this process has the disadvantage of indirect conversion of alpha-IP to KIP as well as lower efficiency and selectivity attributable to the oxidant used.
In U.S. Pat. No. 3,960,966, Widmer et al disclose a process of manufacturing KIP by the oxidation of alpha-IP. The reaction takes place in an oxygen atmosphere and a metal catalyst is used. This invention differs from applicants' in that hydroperoxides are not employed. Lower selectivity is achieved here, and unwanted side products result. Also, this process suffers in that large amounts of catalyst (a significant portion of which is not retrievable) must be employed.
In U.S. Pat. No. 3,944,620, Becker et al disclose a process for preparing KIP from alpha-IP. Here as well, the oxidant is gaseous oxygen and a metal catalyst is employed. The process occurs, at least in part, by the two-step process described above. Unlike applicants' invention, this process also suffers from low efficiency.
In recent years, hydroperoxides have been used in the production of specialty organic chemicals. These oxidants often provide more efficient and selective oxidation reactions. Higher selectivity reduces or eliminates the generation of various side-products. These side-products can affect processing, product purity, and may raise other environmental concerns.
Reactions using tert-butyl hydroperoxide ("TBHP") as an oxidant in KIP production have been reported by Hosokawa et al in Chem. Lett., pp. 1081-1082 (1983). The reactions were catalyzed by Pd(OAc).sub.2 in an air atmosphere. Benzene was used as a solvent.
The present invention is an improved method of alpha-IP to KIP synthesis. The reaction is a one step process in which the isomerization of alpha-IP to beta-IP has been eliminated. Hydroperoxides have proven to be effective oxidants. Applicants catalysts and solvent systems have likewise proven to be a significant improvement in the art. Applicants have solved the problems of inefficiency and low selectivity associated with KIP synthesis in the prior art.